I use one of these style of racks. They come in chrome or black and sell under various names for use in restaurant kitchens, etc.
http://www.foodservicewarehouse.com/kitchen/mobile-shelving-units/c26080.aspxThey have tall & narrow versions and wider, shorter units. The tall narrow units are actually two narrow units fastened together (the long vertical tubes screw into one another). They can take an unlimited number of shelves and will support CRAZY weight levels. You can also shorten them as you see fit (if say low ceilings) with a pipe cutter on the tubes. Remove top caps, cut tubes to same length, re-install caps.
The shelves are adjustable in height w/locking collars at each shelf corner and you can get soft, large diameter locking, no-mar casters that screw into the leg bottoms with app. 1/2" bolts IIRC.
I use a boatload of each type around here for storing photo, garage and household gear and use 1/2 of a tall unit on locking casters with three shelves as a tethering cart - very solid, smooth and has handled a lot of location work (inside). Can also McGyver the crap out them or knock them down (not a fun job if up with some weight on them for any time - the shelves really LOCK into position) for compact transport.
App. $100 ea. in NA at Home Depot or a bit more at any restaurant supply shop.
